However, as it is well known, nucleotide sequences and proteins are complex molecules which may be produced from biological sources, most usually from genetically engineered organisms or cell cultures. Furthermore, the procedures for the production of nucleotide sequences and proteins can be complicated, labour intensive and costly. Furthermore, pharmacological properties and other aspects of the function of some proteins—such as immunoglobulins derived from non-human biological sources—and nucleotide sequences may frequently differ in important ways from the activity of the corresponding natural human immunoglobulins produced in human cells. By way of background information, an immunoglobulin is a member of a family of related multimeric proteins which are normally secreted from cells of the B-lymphocyte lineage of a vertebrate, whose typical function is to bind specifically with a region of a macromolecule identified as non-self. Immunoglobulins represent a major component of the immune response repertoire of the organism and are synonymous with “antibodies”.
One major cause of such differences in activity may be due to variations in the pattern of glycosylation of proteins derived from different spaces (reviewed in Bebbington 1995; In Monoclonal Antibodies: the second generation ed. H. Zola pg 165-181). Furthermore, systemic administration of proteins (especially those containing toxin domains) and nucleotide sequences can induce additional pharmacokinetic and toxicological problems (reviewed in Scheinberg and Chapman 1995. In Monoclonal antibodies (ed. Birch and Lennox) Chapter 2.1).